Apple had their pick of kernels when transitioning from OS 9 to OS X, and they chose to create their own kernel based on Mach 3.0. Was that really the best decision or did Apple make a huge mistake? At the time Linux was gaining support and developing rapidly, while development on Mach had pretty much ended two years earlier. This article makes a case for Apple using the Linux kernel in a future version of the Mac OS.

You're right, I don't offer enough reasons for Apple to make the switch. I sort of gloss over what I consider the biggest advantage: the enterprise market. Apple has shown interest in the market with Xserve and Xserve RAID, but for the enterprise to take Apple seriously, they're going to need a lot more support. Linux has that support and performance now. Businesses spend way more money than consumers, so this is a market that has huge revenue potential for Apple, especially now that they've got a decent partner (Intel) for producing high-end machines in volume.

Linux is not the salvation to all our needs. When facts come into the matter what is important to a successful comercial client AND server OS is that you (as a developer) want to have complete control of the things that are crucial to have a working system. Linux will never (unless dual-licensed) offer that to Apple. Do you honestly think that Apple would even consider for more than half a second to release the code to Aqua?! Quartz or CoreWhatnot?

The type of enterprise computing you are talking about is not and most likely never will be Apples market while Jobs is at the helm. That market just isn't sexy enough and require not support from software developers but support *MAINLY* from the hardware manufacturer (i.e. Apple). It's gonna cost a bit too much to be in the high availability server rooms without any real payoffs. Apple is more about selling in large numbers.

The hardware support you mention (i.e third party drivers etc)... well let's just say that hardware support was never much of an issue for Mac OS before and I suspect it will be an even lesser issue with Mac OS X x86.

Given as a whole, I honestly cannot think of any compelling reason for Apple to switch to Linux.

That said, xnu is not FreeBSD and neither the best kernel/subsystems around but they have proven to be more than good enough and frankly. That is what matters, especially if you also get to keep control.